2" Aura Whisper Waveguide Loaded

[davepellegrene]

I had someone send me the Aura to do some testing in waveguides. I've been wanting to try out some mid's just to see what would happen. I figured this would be a good one since it was only 2". Pretty interesting results.

This is in an 8" round guide 2" deep with a throat of 1-1'4". This fits over the surround and is the same size as the cone. I have not done a flat baffle test yet for a bench mark but I'm guessing it would be somewhere the same SPL level at 10-12 kHz.
The rise above 10 kHz I think has to do with the dish shape of the cone. Just guessing.
0-90 Degrees.



This is with just using DSP to flatten the response.


I put together a quick crossover and fine tuned with DSP. I can't believe this little thing is holding directivity down to 500 Hz and flat out to 15 kHz. It's also some of the best controlled directivity I've seen in my tests.



Distortion at 85 dbs. That's about it playing it down to 500 Hz.


Wonder how it would mate up to a 10" or 12" woofer? Maybe cross about 800 Hz to get a little more SPL out of it.

Dave

[TN Allen]

Re: 2" Aura Whisper Waveguide Loaded

This is great that you're working with a midrange driver. It seems likely to me that waveguides for midrange drivers have more potential for improving the listening experience than waveguides with tweeters. Carefully designed waveguides with both, have a synergistic effect producing surprising results, especially in the way that improved directivity affects how music sounds. I hope you'll try forming larger guides and testing the effect, and also double guides that intersect.

[davepellegrene]

Re: 2" Aura Whisper Waveguide Loaded

This is great that you're working with a midrange driver. It seems likely to me that waveguides for midrange drivers have more potential for improving the listening experience than waveguides with tweeters. Carefully designed waveguides with both, have a synergistic effect producing surprising results, especially in the way that improved directivity affects how music sounds. I hope you'll try forming larger guides and testing the effect, and also double guides that intersect.

I've always planned to get to the mid guides and testing double guides. It really comes down to time. I've got so many tweeters coming in and guides going out that it's eating up all my spare time. I'm thinking about testing some larger guides like 10"-12" to start. Along with that I want to test them for resonating especially the larger they get. I have found that damping even the smaller guides will change the FR plot so it is with doing. At this point I'm leaving it up to the consumer because there are so many ways to do it. I may eventually offer it as an option. It could be as simple as mounting the guide and filling the back of the baffle with thin set. Cheap and easy. Possibly ad a viscoelastic layer between. Half my orders are over seas so the light weight acrylic is the way to go for shipping. Usually packaging and all is less then 1.4 lbs. with two guides.
Only thing I see limiting on size would be the 4' x 8' sheets that I buy the acrylic in. I can see me now making guides with my 80,000 btu turbo heater.


Dave

[PWR RYD]

Re: 2" Aura Whisper Waveguide Loaded

That's really cool Dave that you are getting so many orders (especially over seas) but it stinks it's consuming so much of your personal time. I don't know if your at the same point yet, but years ago I got so busy assembling engines and porting heads and setting up rear gears I ended up where I didn't want to answer my phone. Sure the money was good and suported my own race car parts. But it really took the fun out of it. Please don't burn yourself or family/friends out.

[TN Allen]

Re: 2" Aura Whisper Waveguide Loaded

"Only thing I see limiting on size would be the 4' x 8' sheets that I buy the acrylic in."

That's an interesting possibility. How large a waveguide/baffle would provide significant benefits? How large would just be wasted effort?

[beaujewel]

Re: 2" Aura Whisper Waveguide Loaded

Hmm... this might give me the motivation to finish my project. I started with a Vifa Ne265, cut the dustcap out and was planning on using an NS2 or small peerless fullrange I had as a large tweeter, using the cone as a waveguide. Got pics somewhere..

[davepellegrene]

Re: 2" Aura Whisper Waveguide Loaded

That's really cool Dave that you are getting so many orders (especially over seas) but it stinks it's consuming so much of your personal time. I don't know if your at the same point yet, but years ago I got so busy assembling engines and porting heads and setting up rear gears I ended up where I didn't want to answer my phone. Sure the money was good and suported my own race car parts. But it really took the fun out of it. Please don't burn yourself or family/friends out.

I've been self employed for quite a while and am pretty good about not burning myself out. My wife is as busy as I am and since we are best friends we always find time to get away and enjoy ourselves. Although I don't see my extended family as much as I should thanks to texting and Facebook I stay pretty close with them between visits.
Thanks for the concern.

[davepellegrene]

Re: 2" Aura Whisper Waveguide Loaded

"Only thing I see limiting on size would be the 4' x 8' sheets that I buy the acrylic in."

That's an interesting possibility. How large a waveguide/baffle would provide significant benefits? How large would just be wasted effort?

I saved some old suspended ceiling light panels that are 2'x4'. They would make for a quick experiment. From what I understand the only limitation to a waveguide is size. So if that's the case with a 27" round guide it should give boost down to 500 Hz. It would be an interesting experiment.

Dave

[TN Allen]

Re: 2" Aura Whisper Waveguide Loaded

I saved some old suspended ceiling light panels that are 2'x4'. They would make for a quick experiment. From what I understand the only limitation to a waveguide is size. So if that's the case with a 27" round guide it should give boost down to 500 Hz. It would be an interesting experiment.

Dave

It would be interesting, probably fun too. I've tried 14", which seems to make a difference over 10-12". How deep would you make it? I'm not certain whether midrange guides should be proportionally deeper than tweeter guides, or kept at about the same depth to maintain the drivers in about the same plane behind the baffle surface.

[davepellegrene]

Re: 2" Aura Whisper Waveguide Loaded

I made up a 10x14 flat baffle today to mount the Whisper to. I used a piece of 3/8" thick plywood which fit around the flange to make it perfectly flush to the baffle.

0-90 degrees


I thought this was interesting as I was comparing different axises. These measuremnts are comparing on axis and 60 degrees off axis. between flat baffle in red, 8' guide raw measurement in black and 8" guide with XO and EQ in blue. There is a dip in the waveguide response at 10 kHz of about 3 dbs so to remove this lowers the sensitivity to about 82dbs. The flat baffle measurement was quite good with no crossover components. You could virtually use this as a full range driver without a crossover. What I was amazed with on the guided measurements is how good the controlled directivity is. Its almost a perfect 10 dbs between on axis and 60 degrees down to the cut off of the guide at 1.5 kHz. 1.5 kHz also seems to be the baffle step spot for the 10" wide baffle. Shows pretty clear in the raw measurements. Probably why I'm having such a hard time when crossing the 8" guide on the 10" baffle at 1.5 kHz.


This is with the flat baffle EQ'd down to match the waveguide FR. Top is the flat baffle and bottom is the 8" guide. I'm not sure why the roll off is different between the two below 500Hz. I have them matched up perfect on my measurements. Aside from that the difference in distortion is between the 1.5 to 6 kHz range which is from attenuating the boost from the guide.
I wonder why the there is a peak in distortion at the baffle step? I saw this on other driver tests but at the time didn't realize it was at the baffle step.


Dave

[jhollander]

Re: 2" Aura Whisper Waveguide Loaded

Dave, are all the test open back?

[davepellegrene]

Re: 2" Aura Whisper Waveguide Loaded

Dave, are all the test open back?

They are sealed in my test box that is 10x14 by 10" deep with a little foam stuffing in the box. None directly behind them. I'm sure its not a tight seal either

Dave

[Pallas]

Re: 2" Aura Whisper Waveguide Loaded

Oh man, that's cool.

What's their SPL capability compared to something like your Black Box design from say 600-700Hz up?

Also, I notice your measurements don't show the midrange (2kHz or so) cavity resonance I've measured on my Whispers. Do they still have the bugscreens in back or did the owner snip them and wad some material in the cavity under the diaphragm?

[JochenM]

Re: 2" Aura Whisper Waveguide Loaded

That's some cool work, Dave.

Now what about the Dayton RS52 in an 8" guide or the Tangband 3" (75-1558SE) combined with a 0.75" or 1" tweeter also in one of your guides?
Or maybe even a combined/molded guide for both dome-mid and dome-tweeter (like Klein&Hummel/Neumann does with their O410/O500)

[davepellegrene]

Re: 2" Aura Whisper Waveguide Loaded

Oh man, that's cool.

What's their SPL capability compared to something like your Black Box design from say 600-700Hz up?

Also, I notice your measurements don't show the midrange (2kHz or so) cavity resonance I've measured on my Whispers. Do they still have the bugscreens in back or did the owner snip them and wad some material in the cavity under the diaphragm?

Not sure about the resonance but I do think I remember one in the Impedance graph at 2 kHz. Might be another driver I'm working with. I,ll have to check. Impedance graphs are on my other laptop with XP. WT3 doesn't work with my Vista laptop.

Doesn't look like any mods where done and they still have the screen on the back.

This is with a chunk of denim insulation stuffed up against the back of the screen (black) vs open in the sealed box the waveguide is mounted to.


I'll EQ them flat later and see if the distortion changes any.

SPL wise about 85 dbs at 1 meter is about it EQ'd flat and rolled off as shown in the distortion plot above. There's no way they would keep up with my black box speakers. I've not hooked them up to my pro amp but on my Sherwood 200 watt HT amp it will start to clip before the speakers show any siqns of distortion. It's plenty loud in my test room.

Dave